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12/01/2022

Cities and climate change: why low-rise buildings are the future – not skyscrapers
More than half of the world’s 7.8 billion people live in cities and urban areas. By 2050, an additional 2.5 billion will be living there. As that figure continues to climb and ever more people flock to metropolitan areas in the hope of a better life, the big question is: how do we fit everyone in?

It is the job of city developers and urban planners to figure out how to build or adapt urban environments to accommodate the living and working needs of this rapidly expanding population. There is a popular belief that taller, more densely packed skyscrapers are the way forward, because they optimise the use of space and house more people per square metre and limit urban sprawl.

But given the global commitments to emissions-reduction targets and mitigating climate change, is this the most sustainable solution from a carbon-reduction perspective?

Our recent study, which examined whether building denser and taller is the right path to sustainability, busts this myth: we found that densely built, low-rise environments are more space and carbon efficient, while high-rise buildings have a drastically higher carbon impact.

Impact on the environment
We assessed the whole-life cycle of carbon emissions – meaning both operational and “embodied” carbon – of different buildings and urban environments. Operational carbon is generated while a building is in service. Embodied carbon is all the hidden, behind-the-scenes carbon produced during the extraction, production, transport and manufacture of raw materials used to construct a building, plus any produced during maintenance, refurbishment, demolition or replacement.

This aspect is often overlooked, especially in building design, where operational efficiency is always to the fore. The argument for cutting carbon at the design stage has been made by numerous researchers, and it is gaining traction with leading international organisations such as the World Green Building Council. But it’s still something that is largely disregarded, mainly because embodied impact assessment is voluntary, and there is no legislation concerning its inclusion. But it must be advocated for if we are to reach our 2050 emissions targets.

At a global scale, the construction sector is responsible for a significant impact on the environment, as is clear from the graph below. The largest contribution comes from its consumption of energy and resources, which boils down to the design stage – the part of the process that no one is looking at.

Graph showing construction sector's contribution to environmental impacts.
Construction sector’s contribution to environmental impacts. Edinburgh Napier University
Now that new buildings have to be more energy efficient and the energy grid is being decarbonised, this hidden embodied energy varies from 11%-33% for projects such as Passive House designs (a building standard that uses non-mechanical heating and cooling design techniques to lower energy use) to 74%-100% for near-zero energy builds (high performance buildings where the low amount of energy required comes mostly from renewable sources).

Given the focus on driving down the energy impact of day-to-day operations, the proportional share of embodied energy consumption has been driven up. So as energy demand becomes lower when the building is in use, the materials and activities required to build it in first place produce proportionally more impacts across the building’s lifespan. For example, low and near-zero energy buildings are made by improving insulation and using more materials and additional technologies, which greatly increases the hidden energy impact and carbon cost.

Moving to a smaller scale, the embodied carbon share across construction materials shows that minerals have the largest proportion by far, at 45%. The graph below shows the breakdown of materials, where concrete dominates in terms of hidden carbon contribution. This is important because skyscrapers rely heavily on concrete as a structural material. So the type of materials we use, how much we use, and how we use them is crucial.

Graph showing the carbon contribution of different minerals used in construction.
The carbon contribution of different minerals used in construction. Edinburgh Napier University, Author provided
How we can fix it
We developed four different urban scenarios shown in the graph below, based on data from real buildings: high-density, high-rise (HDHR) which are tall and close together; low-density, high-rise (LDHR) which are tall but more spread out; high-density, low-rise (HDLR) which are low and close together; and low-density, low-rise (LDLR) which are low level and more spaced out.

To do this, we split the building stock into five main categories: non-domestic low-rise (NDLR); non-domestic high-rise (NDHR); domestic low-rise (DLR); domestic high-rise (DHR); and terraced/house. We gathered numerous data, including height, number of storeys, building footprint (the land area the building physically occupies), facade material and neighbouring constraints. This includes the number and area of blocks and green spaces within one square kilometre, average street width and average distance between buildings.

A graphic showing four different urban environments contained in the research study.
Four urban scenarios analysed in the study. Edinburgh Napier University, Author provided
These parameters were all fed into a computer model to analyse the data looking at the following:

1. How whole life-cycle carbon changed based on the buildings and the number of people accommodated within an area of 1km².

2. How whole life-cycle carbon changed due to an increasing population based on four fixed population sizes – 20, 30, 40 and 50 thousand people – and the land use required to accommodate them under the four different urban scenarios.

Our findings show that high-density low-rise cities, such as Paris, are more environmentally friendly than high-density high-rise cities, such as New York. Looking at the fixed population scenarios, when moving from a high-density low-rise to a high-density high-rise urban environment, the average increase in whole life-cycle carbon emissions is 142%.

A panorama of New York's iconic skyscrapers.
New York’s densely packed skyscrapers. Sean Pavone/Shutterstock
Equating this to the potential savings per person, based on the fixed population size, building high-density low-rise offers a saving of 365 tonnes of CO₂ equivalent per person compared with high-density high-rise.

It’s time for urban planners to start embedding this new understanding of the whole carbon life-cycle of a building, balancing the impact of urban density and height while accommodating expanding populations. To achieve urban sustainability the world will need more Parises and fewer Manhattans.

12/01/2022

Inclusion, walkability will be key to rebuilding cities after the COVID-19 pandemic
Cities emerged as the epicentres of the COVID-19 pandemic: roughly 90 per cent of COVID-19 infections worldwide were reported in urban settings. And poor urban neighbourhoods were hit especially hard.

Researchers frequently attributed the vulnerability of cities to high population density, overcrowding and poor air circulation. The vulnerability of cities during the COVID-19 pandemic has highlighted the need to create sustainable cities that promote health.

To address the pandemic, municipal governments around the world have changed their approaches to urban planning.
Less density, more diversity
As sociologists interested in urban settings, we examined how the physical environment of neighbourhoods shaped the spread of COVID-19 in Toronto. Our findings suggest a few things cities should keep in mind as they rebuild following the pandemic.

First, we should create more walkable neighbourhoods. COVID-19 spread at a much slower pace in highly walkable neighbourhoods. Residents in these neighbourhoods can travel shorter distances on wider and better maintained sidewalks, which may reduce their exposure to the COVID-19 virus.

Read more: The pandemic highlights the importance of walkable and wheelable neighbourhoods

An older apartment building with a canadian flag flying from one balcony
Higher population density increased the spread of COVID-19 in low-income neighbourhoods, but lowered the infection rate in more affluent neighbourhoods. (Shutterstock)
Second, we should reduce the number of overcrowded households. Soaring real estate prices have forced many socio-economically disadvantaged families into overcrowded housing. Space constraints in these housing units may make it more difficult for residents to practice adequate physical distancing. It may have also deprived them of the space necessary to isolate if they contracted the virus. These factors may have increased their risk of contracting COVID-19. Increasing the supply of affordable housing may hold the key to reducing the urban poor’s vulnerability to infectious diseases.

Third, we should increase the number of mixed-income housing units and better integrate our neighbourhoods. COVID-19 spread much faster in lower-income neighbourhoods. Housing affordability may have pushed out disadvantaged families from higher-income neighbourhoods and forced them to settle in lower-income areas with fewer amenities.

Displacement and higher density due to limited housing affordability may have increased the concentration of residents who were exposed to the COVID-19 virus. Residents of low-income neighbourhoods are more likely than their peers in affluent neighbourhoods to live in close proximity to someone with a COVID-19 infection.

Tailored responses
Residents of low-income neighbourhoods rely more on neighbourhood amenities than their peers in affluent neighbourhoods because they have fewer personal resources at their disposal. And even when communities have the same amenities, those in lower-income neighbourhoods are more likely to be poorly maintained. For example, lower-income neighbourhoods may lack wide and well-maintained sidewalks.

They also have fewer health-promoting amenities, such as grocery stores with fresh produce or high quality health care facilities. Therefore, a neighbourhood’s physical environment contributes to the spread of COVID-19 differently in lower and higher income neighbourhoods.

Our study reveals that population density increased the spread of COVID-19 in low-income neighbourhoods, but it lowered the infection rate in high-income neighbourhoods. In more affluent neighbourhoods, even high-density apartment buildings come with amenities and protections — like better ventilation systems and additional staff to properly sanitize common areas — that similarly dense buildings in lower-income neighbourhoods lack.

Read more: As coronavirus forces us to keep our distance, city density matters less than internal density

Similarly, green space mitigates the spread of COVID-19 in lower-income, but not higher-income, neighbourhoods. Housing units in low-income neighbourhoods are likely smaller, overcrowded, less well-maintained and have poorer ventilation. Residents of low-income neighbourhoods may thus face greater difficulty adhering to stay-at-home policies. Large green spaces in such neighbourhoods may provide a safe space where residents can get clean air and safely practice social distancing.

Groups of people sit on the grassy ground behind a modern building
Building more urban green spaces will allow people to socialize safely. (Shutterstock)
Furthermore, neighbourhood walkability helps mitigate the spread of COVID-19 more in lower-income neighbourhoods than in higher-income neighbourhoods. This pattern likely emerges because residents of low-income neighbourhoods are less likely than their counterparts in affluent neighbourhoods to own cars. They are more likely to rely on public transportation for errands that cannot be completed on foot. For residents of low-income neighbourhoods with poor walkability, running errands may require longer trips and making multiple transfers in the public transportation system.

After the pandemic
The COVID-19 pandemic has highlighted the need for us to build sustainable cities that promote health and reduce the vulnerability to infectious diseases among their residents. Future urban planning efforts should not adopt a one-size-fits-all approach. Instead, they should tailor the rebuilding process to meet the diverse needs of residents of lower and higher income neighbourhoods.

Specifically, rebuilding efforts should prioritize low-income neighbourhoods and remedy their high population density, construct more green spaces and improve their walkability.

12/01/2022

3 in 4 people want to ride a bike but are put off by lack of safe lanes
Cycling is healthy and sustainable, but only 1.7% of trips in Melbourne are made by bike. Car use has soared since lockdowns were lifted.

We surveyed over 4,000 Victorians and found more than three-quarters are interested in riding a bike, but only in infrastructure that separates people from cars (such as off-road paths or protected bike lanes).

This proportion is far higher than previously thought, highlighting a huge opportunity to increase bike-riding rates by building separated bike lanes.

Our study, published in the Journal of Transport and Health, found high levels of interest in bike riding in groups with traditionally lower participation, including women and people living in outer-urban fringe areas.

However, these areas tend to have less access to safe, protective and supportive infrastructure than their higher socioeconomic counterparts.

Read more: Bike kitchens: the community-run repair workshops that help build a culture of cycling

A person rides in the fog past some cars.
Cycling is healthy and sustainable, but only 1.7% of trips in Melbourne are made by bike. TRACEY NEARMY/AAP
Infrastructure is key
Previous research has shown that how unsafe someone feels when riding a bicycle – particularly in the presence of motor vehicle traffic – is the key barrier to cycling.

Too much existing bike infrastructure is simply a strip of white paint; 99% of existing on-ride bike infrastructure in Melbourne is made up of painted bike lanes, which result in closer motor vehicle passes and do not protect cyclists from potential injury.

Providing high quality, connected and protected bike lanes or paths that separate people on bikes from motor vehicle traffic would greatly increase cycling rates in Melbourne.

A person rides down a bike lane.
Many people are interested in riding, but only in paths separate from cars. DAN PELED/AAP Image
Bike infrastructure must work for women, as well as men
For every woman that rides a bike in Melbourne, there are two men doing the same.

Despite lower participation, our study showed two-thirds of women are interested in riding a bike, and over half own a bike. Research suggests women are more likely than men to feel vulnerable to harassment by drivers when riding, may need more storage space than a bike usually provides, and may have more care-giving responsibilities than men. Differing perceptions of risk are also a factor.

Women have different infrastructure preferences to men, with a high preference for bike paths or lanes physically separated from motor vehicle traffic.

Taken together, these factors contribute to a pattern where many city bike paths and lanes are designed for the needs and confidence levels of male cyclists.

Common to many cities in Australia and around the world is what’s known as the “radial planning fallacy”, where transport systems are designed to optimise trips from outer-urban areas to city centres or businesses – rather than to facilitate local trips.

The majority of protected bike paths or lanes in Melbourne are radial in design, with a lack of connectivity between existing paths.

This kind of planning does not support the needs of many actual or aspiring cyclists, particularly women who tend to have more varied trips around places such as school, local shops and other locations close to home.

A woman cycles on the street.
We must plan bike infrastructure that supports the needs of women, as well as men. Shutterstock
Outer suburbs are losing out
Despite lower participation, we found that interest in bike riding is high in the outer urban fringe areas of Melbourne.

These areas also have the lowest level of access to safe and comfortable bike infrastructure.

People who are inexperienced or new to bike riding prefer bike paths or lanes that are physically separated from motor vehicle traffic.

But a lack of infrastructure dedicated to active transport, coupled with longer distances to essential services, means people living in outer-suburbs are often required to drive long distances.

A cyclist is nearly hit by a car on a road
Too much existing bike infrastructure is simply a strip of white paint. CHRISTOPHER SAMUEL/AAP
To address these health and transport inequities, it’s essential we plan and build protected and connected bike infrastructure across Melbourne, including new urban growth areas.

As well as boosting health outcomes, optimising social connection and reducing transport inequities, this would also contribute toward meeting Australia’s net-zero emissions targets.

12/01/2022

12/01/2022